The present invention relates to integrated circuit wafer processing equipment and, more specifically, to an automatic wafer loading and pre-alignment system for integrated circuit wafer-mask Aligners. Manually operated and automatic Aligners for aligning a printed circuit wafer to a mask are well known in the integrated circuit processing field. Representative examples of mask alignments systems include the Models CA-400 and CV-100 mask Aligners manufactured and sold by the Cobilt Division of The Computervision Corporation, 1135 Arques Ave. Sunnyvale, Calif. 94086. The patent literature contains substantial information on mask alignment systems e.g. U.S. Letters Pat. Nos. 3,587,334; 3,604,546; 3,617,751; 3,622,856; 3,660,157; and 3,671,748.
In existing mask alignment systems, the individual, unexposed wafer is manually loaded into a chuck which is positioned on the Aligner turntable. The turntable carrying the chuck and wafer is then rotated into the alignment and exposure position. After exposure, the turntable is again rotated to allow the operator to manually remove the now exposed wafer from the chuck. The individual, manual loading and handling of both the unexposed and exposed wafers is undesirable both in terms of subjecting the wafer to excessive handling as well as increasing the probability of physical damage to the wafer.
It is, accordingly, a general object of the present invention to provide an automatic wafer loading and pre-alignment system for integrated circuit wafer-mask Aligners which eliminates individual wafer handling while achieving accurate automatic pre-alignment and throughput.
It is a specific object of the invention to provide an automatic wafer loading and pre-alignment system which can be interfaced with existing manual and automatic mask Aligners.
It is another object of the invention to provide indexable carriers for storing the unexposed and exposed wafers.
It is a feature of the invention that the unexposed and exposed wafer carriers are accurately indexed in synchronization with each other.
It is still another object of the invention to provide feed and return track systems for transporting the unexposed and exposed wafers, respectively, in which the two track systems have a common portion between the wafer carriers and a wafer pre-alignment station.
It is another feature of the invention that the wafer carriers, feed track systems and wafer pre-alignment station can accommodate different sized wafers.
It is still another object of the invention to provide a wafer pre-alignment system which produces accurate and repeatable pre-alignment of unexposed wafers on the Alignert's turntable.